Elastomeric compositions and their applications

Abstract

The present disclosure generally relates to thermally conductive silicone compositions and elastomer and gels prepared from a multi-part condensation cure composition catalysed by titanium or zirconium based catalysts. Applications of the resulting thermally conductive silicone elastomers and gels are also considered.

The invention claimed is: 
     
       1. A reversion free multi-part, condensation curable, thermally conductive silicone adhesive composition comprising:
 (i) at least one condensation curable silyl terminated polymer having at least one hydroxyl functional group per molecule; 
 (ii) a cross-linker selected from the group of:
 silanes having at least 2 hydrolysable groups per molecule, and/or 
 silyl functional molecules having at least 2 silyl groups, each silyl group containing at least one hydrolysable group or a mixture thereof, 
 
 (iii) at least one condensation catalyst selected from the group consisting of titanates and/or zirconates; and 
 (iv) one or more thermally conductive fillers, present in an amount of from 70 to 93% of the composition by weight;
 wherein polymer (i), cross-linker (ii) and condensation catalyst (iii) are not contained in the same part; and 
 wherein the molar ratio of total silicon-bonded hydroxyl groups to total hydrolysable groups is between 0.2:1 to 2:1 using a silane cross-linker (ii) or 0.2:1 to 10:1 using a silyl functional molecule cross-linker (ii) and the molar ratio of condensation catalyst (iii) M-OR functions to the total silicon-bonded hydroxyl groups is between 0.01:1 and 0.5:1, where M is titanium or zirconium, and R is an aliphatic hydrocarbon group. 
 
 
     
     
       2. The reversion free multi-part, condensation curable, thermally conductive silicone adhesive composition in accordance with  claim 1 , wherein the composition is stored in two parts and where the parts are divided as follows:
 a) polymer (i) and cross-linker (ii) in one part and polymer (i) and condensation catalyst (iii) in the other part; or 
 b) cross-linker (ii) in one part and polymer (i) and condensation catalyst (iii) in the other part; or 
 c) a first polymer (i) and cross-linker (ii) in one part and a second polymer (i) and condensation catalyst (iii) in the other part; or 
 d) polymer (i) in one part and cross-linker (ii) and condensation catalyst (iii) in the other part. 
 
     
     
       3. The reversion free multi-part, condensation curable, thermally conductive silicone adhesive composition in accordance with  claim 2 , wherein the thermally conductive filler (iv) is present in both parts of the composition, or is in a base part with polymer (i). 
     
     
       4. The reversion free multi-part, condensation curable, thermally conductive silicone adhesive composition in accordance with  claim 1 , wherein the thermally conductive filler (iv) is selected from the group consisting of silver powder, aluminum powder, aluminum oxide powder, zinc oxide powder, graphite nitride, and mixtures thereof. 
     
     
       5. The reversion free multi-part, condensation curable, thermally conductive silicone adhesive composition in accordance with  claim 1 , wherein the thermally conductive filler (iv) is:
 i) is mixture of aluminum oxides; or 
 ii) a mixture of pre-treated aluminum oxides different sizes. 
 
     
     
       6. The reversion free multi-part, condensation curable, thermally conductive silicone adhesive composition in accordance with  claim 4 , wherein the thermally conductive fillers (iv) are differentiated by average particle size with a mixture of two or more of a) to c) below:
 a) a thermally conductive filler (iv) having an average particle size value of from 20 to 80 micrometers; 
 b) a thermally conductive filler (iv) having an average particle size value of from 2 to 10 micrometers; 
 c) a thermally conductive filler (iv) having an average particle size value of from 0.1 to 1 to micrometers. 
 
     
     
       7. A reversion free thermally conductive silicone adhesive cured from the reversion free multi-part, condensation curable, thermally conductive silicone adhesive composition in accordance with  claim 1 . 
     
     
       8. The reversion free thermally conductive silicone adhesive in accordance with  claim 7 , in the form of a gel or an elastomer. 
     
     
       9. A sealant for an electrical or electronic part, comprising the reversion free thermally conductive silicone adhesive in accordance with  claim 7 . 
     
     
       10. An electrical or electronic part encapsulated/potted with the gel of  claim 8 . 
     
     
       11. A method of making an adhesive, the method comprising:
 intermixing a multi-part adhesive composition to form a mixture; and 
 curing the mixture to form the adhesive; 
 wherein the multi-part adhesive composition is the reversion free multi-part, condensation curable, thermally conductive silicone adhesive composition according to  claim 1 . 
 
     
     
       12. Electrical or electronic equipment provided with a member made from curing the reversion free multi-part, condensation curable, thermally conductive silicone adhesive composition according to  claim 1 . 
     
     
       13. A heat radiating member for electric and electronic devices made from the reversion free multi-part, condensation curable, thermally conductive silicone adhesive composition according to  claim 1 . 
     
     
       14. The heat radiating member in accordance with  claim 13 , in the form of an interface between a semiconductor electronic component and a metal heat sink. 
     
     
       15. The reversion free multi-part, condensation curable, thermally conductive silicone adhesive composition in accordance with  claim 1 , wherein polymer (i) has at least 2 hydroxyl functional groups per molecule. 
     
     
       16. The reversion free multi-part, condensation curable, thermally conductive silicone adhesive composition in accordance with  claim 1 , wherein cross-linker (ii) is selected from the group consisting of silanes having at least 3 hydrolysable groups per molecule.